april 2020 underwater noise...the impact of underwater ship noise on marine life in deep oceans as a...

GUIDE FOR THE CLASSIFICATION NOTATION

UNDERWATER NOISEAPRIL 2020

American Bureau of ShippingIncorporated by Act of Legislature ofthe State of New York 1862

© 2020 American Bureau of Shipping. All rights reserved.1701 City Plaza DriveSpring, TX 77389 USA

ForewordThis Guide sets forth requirements for the optional underwater noise notation UWN (Type) and UWN+(Type). It is applicable to self-propelled commercial and research vessels. This Guides outlines the processand criteria to obtain the notation. It also provides requirements on acoustic instrumentation, test siteconditions, measurement procedures for the underwater noise measurement, as well as a description of thepost-processing activities to be carried out for the resulting data sets collected from the measurement.

Both IMO and the European Union (EU) have made efforts to support the reduction of underwater radiatednoise (IMO MEPC.1/Circ.833 Guidelines for the Reduction of Underwater Noise from CommercialShipping to Address Adverse Impacts on Marine Life and EU Marine Strategic Framework Directive,2008/56/EC) to address concerns about the underwater noise pollution affecting marine life and habitats.

The guidelines contained in IMO MEPC.1/Circ.833 are technical advice/guidance for designers,shipbuilders, and ship operators on the reduction of underwater noise due to commercial shipping. ABSrecognized the need for continuing work to develop optional notations to establish the baseline underwaternoise levels for vessels and quantify the relationship between individual ship noise levels and the regionalambient noise level reductions. It is anticipated that there will be future development work by the MEPCon this issue.

The EU Marine Strategic Framework Directive (MSFD), 2008/56/EC, which entered into force on 15 July2008, addresses the protection of the marine environment. It requires EU Member States to achieve a GoodEnvironmental Status (GES) in all the EU waters by 2020. It sets out 11 high-level environmentalDescriptors for achieving the GES [EC 2010], and the 11th Descriptor includes underwater noise. With thisDirective being enforced, underwater noise from ships is an issue of great relevance, and all MemberStates are obliged to provide an evaluation of the GES of their marine waters based on the descriptors andtargets.

In response to the above regulatory initiatives and the growing interest in the quantification andminimization of underwater radiated noise from commercial shipping in the current marine industry, ABSrecognizes the need for the development of this ABS Guide for the Classification Notation UnderwaterNoise with the objective to assist vessel operators to address the underwater noise control aspect.

This Guide becomes effective on the first day of the month of publication.

Users are advised to check periodically on the ABS website www.eagle.org to verify that this version ofthis Guide is the most current.

We welcome your feedback. Comments or suggestions can be sent electronically by email [email protected].

ABS GUIDE FOR THE CLASSIFICATION NOTATION UNDERWATER NOISE • 2020 ii

GUIDE FOR THE CLASSIFICATION NOTATION

UNDERWATER NOISE

CONTENTSSECTION 1 General..................................................................................................6

1 Introduction.....................................................................................63 Application...................................................................................... 65 Scope..............................................................................................77 Basis and Process of Obtaining a Notation.................................... 7

7.1 Basis.................................................................................. 77.3 Process for Obtaining a Notation.......................................7

9 Alternatives.....................................................................................811 Major Modifications.........................................................................813 Definitions.......................................................................................915 Abbreviations................................................................................ 11

FIGURE 1 Flow Diagram for Obtaining ABS Underwater NoiseNotation UWN (Type) or UWN+ (Type)................................. 8

SECTION 2 Documentation and Engineering Review........................................ 121 Plans and Documentation for Information.................................... 123 Engineering Review......................................................................12

TABLE 1 Underwater Noise Measurement Plan................................. 13TABLE 2 Underwater Noise Measurement Report..............................14

SECTION 3 Underwater Noise Requirements..................................................... 151 General.........................................................................................153 Underwater Noise (UWN) Requirements for Commercial

Vessels......................................................................................... 155 Underwater Noise (UWN) Requirements for Research Vessels...167 Underwater Noise Plus (UWN+) Requirements for

Commercial Vessels..................................................................... 17

TABLE 1 UWN Limits for Commercial Vessels................................... 16TABLE 2 UWN Limits for Research Vessels....................................... 17TABLE 3 UWN+ Limits for Commercial Vessels................................. 18

FIGURE 1 Allowable UWN Limits for Commercial Vessels...................16

ABS GUIDE FOR THE CLASSIFICATION NOTATION UNDERWATER NOISE • 2020 iii

FIGURE 2 Allowable UWN Limits for Research Vessels.......................17FIGURE 3 Allowable UWN+ Limits for Commercial Vessels.................18

SECTION 4 Instrumentation for Measurement....................................................191 Introduction...................................................................................193 Hydrophones and Signal Conditioning......................................... 19

3.1 Required Characteristics of a Hydrophone......................193.3 Deployment of Hydrophones........................................... 193.5 Hydrophone(s) Array Deployment Geometry.................. 223.7 Signal Conditioning..........................................................23

5 Data Acquisition and Recording................................................... 237 Sound Data Processing and Display System............................... 24

TABLE 1 Performance Requirements of Hydrophones.......................19

FIGURE 1 Deployment Using a Support Vessel....................................20FIGURE 2 Deployment Using a Surface Buoy with an Independent

Recorder.............................................................................. 21FIGURE 3 Deployment using Bottom Mounted System (Anchor

with Sub Surface Buoy)........................................................22FIGURE 4 Hydrophone Array Deployment with Respect to Vessel

under Test............................................................................ 23

SECTION 5 Underwater Noise Measurement and Survey..................................251 General.........................................................................................25

1.1 Measurement Protocols...................................................251.3 Measurement Plan...........................................................251.5 Background Noise Measurement.................................... 261.7 Distance Measurement....................................................261.9 Performance of Underwater Noise Measurement........... 261.11 Other Auxiliary Measurements and Data.........................26

3 ABS Recognized External Specialist for Underwater NoiseMeasurement................................................................................27

5 Survey...........................................................................................277 Test Site Requirements.................................................................27

7.1 Depth of the Water...........................................................287.3 Weather/Sea Surface Conditions.................................... 28

9 Test Conditions of Vessel..............................................................289.1 Operation Condition.........................................................289.3 Loading Condition............................................................289.5 Test Course......................................................................29

11 Measurement Test Sequence.......................................................2911.1 General............................................................................ 2911.3 Sea Trial Procedure.........................................................29

ABS GUIDE FOR THE CLASSIFICATION NOTATION UNDERWATER NOISE • 2020 iv

11.5 Underwater Noise Measurement Test Sequence............ 3013 Processing and Analysis of Measured Data.................................31

13.1 Background Noise Correction..........................................3113.3 Bottom Effect Correction..................................................3213.5 Sensitivity Adjustment......................................................3213.7 Distance Correction......................................................... 3213.9 Power-averaged of the Sound Source Level from all

Hydrophones................................................................... 3313.11 Arithmetic Average of the Sound Source Level of the

Four Runs under the Same Operation Condition............ 3315 Measurement Report....................................................................34

TABLE 1 Current Underwater Noise Measurement Standardsand Other Related Measurement Standards....................... 25

TABLE 2 Signal-Plus-Noise-to-Noise Ratio Conditions.......................31

FIGURE 1 Underwater Noise Measurement Configuration – BeamAspect Test Course..............................................................29

APPENDIX 1 Underwater Noise Control.................................................................351 Introduction...................................................................................353 Propeller Noise Control.................................................................355 Machinery Equipment Noise Control............................................ 35

APPENDIX 2 Underwater Noise Measurements Data Sheet.................................36

APPENDIX 3 References..........................................................................................40

ABS GUIDE FOR THE CLASSIFICATION NOTATION UNDERWATER NOISE • 2020 v

S E C T I O N 1 General

1 IntroductionThe impact of underwater ship noise on marine life in deep oceans as a result of the global increase ofvessel numbers, vessel size, and propulsion power has recently become an emerging issue in the marineindustry. Ships generate underwater noise over a broad range of low frequencies, particularly from thepropeller, machinery, and hull movements. The radiated underwater noise poses a potential threat to marinemammal behavior and/or induces stress responses as it may interfere with their hearing of natural signalsfor communication, feeding, socializing, prey detection, and orientation in the water.

Historically, underwater radiated noise from commercial vessels was not a key area of consideration inship design and construction. However, with the increased attention and efforts made by internationalregulatory bodies such as IMO and the EU to minimize the adverse effect of underwater radiated noisefrom commercial vessels on marine mammals (see, for instance, IMO MEPC.1/Circ.833; EU MSFD2008/56/EC), ABS recognized the need for developing this Guide. The intent of this Guide is to providethe ship owners with optional notations to help address underwater radiated noise.

This Guide has been developed with the objective of promoting an environmentally-friendly ship design,assisting the specific vessel to operate in a “quieter” condition with the aim of reducing the radiatedunderwater noise.

3 Application (1 April 2020)This ABS Guide for the Classification Notation Underwater Noise is applicable to vessels for which oneor multiple optional underwater noise notations listed below has been requested.

UWN (Type) For the vessel that has met the underwater noise criteria specified in this Guide.See 3/3 and 3/5.

UWN+ (Type) For the vessel that has met the more stringent underwater noise criteria specified in this Guide.See 3/7.

Type denotes the type of underwater noise criteria. The following Type notations may be assigned:

T Underwater noise criteria for Transit condition. See 3/3 and 3/7.

Q Underwater noise criteria for Quiet Operation condition. See 3/3 and 3/7.

R Underwater noise criteria for Research Vessels. See 3/5.

A commercial vessel may carry multiple underwater noise notations. The notation UWN (T) and/or UWN(Q) can be assigned provided the vessel can meet the underwater noise criteria under Transit condition fornormal operation and/or Quiet Operation condition for low speed operation in environmentally-sensitiveareas. The minimum vessel speed in the test for the Quiet Operation condition is specified in 5/9.1. Whenthe vessel can meet more stringent underwater noise criteria, notation UWN+ (T) and/or UWN+ (Q) canbe assigned.

For research vessels, there is only one notation applicable, UWN (R).

ABS GUIDE FOR THE CLASSIFICATION NOTATION UNDERWATER NOISE • 2020 6

The Guide is applicable to self-propelled commercial vessels and research vessels that are equipped withship acoustic design technologies in their design and construction to perform specific operations.

The application of this Guide to offshore exploration and production vessels is subject to case-by-casereview by ABS with consideration of specific designs and operational conditions of these vessels.

The notation only focuses on the noise aspect generated during normal/routine ship activities. Other marineactivities, such as seismic surveys or pile driving, which result in loud and short duration noise, are notcovered in the scope of this Guide.

5 ScopeThis Guides outlines the process and criteria to obtain the notation. It provides requirements on acousticinstrumentation, test site conditions, measurement procedures for the underwater noise measurement. Italso provides a description of the post-processing activities to be carried out for the resulting data setscollected from the measurement.

7 Basis and Process of Obtaining a Notation

7.1 BasisThe measurement requirements and criteria in this Guide are based on a combination of the availableinternational regulations and standards, as referenced in Section 5, Table 1, and reviews of researchregarding the effects of underwater radiated noise on marine aquatic life from commercial and researchshipping.

7.3 Process for Obtaining a NotationThe flowchart in Section 1, Figure 1 depicts the process for obtaining a UWN (Type) notation or a UWN+(Type) notation where more stringent requirements are introduced.

The Underwater Noise Measurement Plan, which includes the relevant information and drawings as shownin Section 2, Table 1, is to be submitted to ABS for review before scheduling the underwater noisemeasurement. The intent of this measurement plan is to serve as a primary means of verification that all thenecessary requirements and conditions for carrying out the actual underwater noise measurement duringsea trials are satisfied before carrying out the actual measurement. This includes identifying the ABSRecognized External Specialists for Underwater Noise Measurement, who are companies recognized byABS that are qualified to do underwater noise measurements for the UWN (Type) or UWN+ (Type)notation.

The underwater noise measurement and the data collection process are to be executed by an ABSRecognized Underwater Sound Specialist and witnessed by an ABS Surveyor.

The ABS Recognized External Specialist will post-process the collected measurement data and include theprocessed results in the final measurement report. The other contents that the measurement report is toinclude are indicated in Section 2, Table 2. The final measurement report is to be submitted to ABSEngineering for review.

The UWN (Type) or UWN+ (Type) notation may be issued provided that:

● The underwater noise measurement has been carried out according to the measurement plan approvedby ABS and the procedures as specified in Section 5

● The resulting signature noise source level from the measurement is within the maximum allowableunderwater noise level criteria limits as per Section 3.

Section 1 General 1


FIGURE 1Flow Diagram for Obtaining ABS Underwater Noise Notation UWN (Type) or

UWN+ (Type)

9 AlternativesABS is prepared to consider alternative procedures, methods or arrangements that are based oninternationally recognized codes/standards. When alternate codes and/or standards are proposed,comparative analyses are to be provided to demonstrate equivalency to the criteria that is referred to in thisGuide.

11 Major ModificationsABS is to be notified of any modifications made to major components on the vessel, such as changes to thehull form, the main machinery (including propulsion and large auxiliary equipment) and propellers, whichcontributes to the underwater radiated noise.

ABS will review the scope of the modification and advise the shipyard/owner of the necessity for a new setof measurements to be carried out in accordance to Section 5 of this Guide in order to maintain the existingclass notation.

Section 1 General 1


13 DefinitionsAcoustic Center. The position on the vessel where it is assumed that all the noise sources are co-located asa single point source. In this Guide, it is assumed to be located halfway between the center of the engineroom and the propeller for all test conditions.

Attenuation. The opposite of amplification, which is necessary when voltages to be digitized are beyondthe analog-to-digital converter (ADC) range. This form of signal conditioning decreases the input signalamplitude so that the conditioned signal is within the ADC range. Attenuation is typically necessary whenmeasuring voltages that are more than 10 volts.

Background Noise. Noise from all sources (biotic and abiotic) other than the vessel being tested andmeasured.

Beam Aspect. The direction to either side of the vessel under side.

Broadband. In the context of this Guide, “broadband” refers to sound energy over the one-third octavefrequency band. In order to compare broadband measurements, the underwater acoustics communitygenerally report broadband levels in one-third octave frequency bands.

Cavitation Inception Speed. Vessel speed at which a propeller starts to cavitate.

Closest Point of Approach (CPA). The point during a test run where the horizontal distance from theacoustic center of the vessel under test is the closest to the hydrophone(s). This position on the straight linecourse is referred as the CPA point. The distance at the closest point of approach is defined by the symboldCPA. See Section 5, Figure 1.

Data Window Length (DWL). The distance between the start data point and the end data point, given as2 × dCPA × tan 30 . See Section 5, Figure 1.

Data Window Period (DWP). The time window the test vessel to travel the data window length (DWL) at aspecified test speed (ν) given by DWP = DWL/ν.

Decibel (dB). A relative unit for the intensity of a sound wave to a reference intensity. In underwatersound, it is expressed using the logarithmic decibel scale referenced to 1 micro-Pascal, as dB re 1 μPa(1.45 × 10-10 psi).

Effective Sound Pressure. The root mean square of the sound pressure of the source over a given interval oftime or space.

End Data Point. The position where the data recording is ended when the acoustic center of the test vesselpassed this point. It is typically at a distance half DWL past the CPA point. This point is also known as the“Stern CPA”. See Section 5, Figure 1.

Ending Point of Test Range. The ending location of a test run at a distance twice the data window length(DWL) after the CPA point. See Section 5, Figure 1.

Far Field. A region in free space, away from the sound source. In this region, the sound pressure is inphase with the sound particle velocity. In the far field, the direct field radiated by most machinery sourceswill decay at the rate of 6 dB each time the distance from the source is doubled.

Free Field. A sound field region where sound may propagate freely without any form of obstruction. Inpractice, a free field can be said to exist if the direct sound is 6 dB, or preferably 10 dB, greater than thereverberant or reflected sound.

Section 1 General 1


Hydrophone. A transducer that produces electric signals in response to water borne acoustic signals. Forthe purpose of this Guide, “hydrophone” could also refer to the underwater microphone or electro-acoustictransducer.

Narrow Band. The entire frequency range is divided into subsections with equal bandwidth. Thebandwidth is usually 1 Hz.

Near Field. A part in the sound field region which is close to a source where the sound pressure is not inphase with the sound particle velocity. In this region, the sound field does not decrease by 6 dB each timethe distance from the source is increased (as it does in the far field). The near field is limited to a distancefrom the source equal to about a wavelength of sound or equal to three times the largest dimension of thesound source (whichever is the larger).

Omni-directional Hydrophone. Underwater sound pressure transducer that responds equally to sound fromall directions.

One-third Octave Band. The logarithmic frequency band whose upper limit is 21/3 (1.26) times the lowerlimit, and the center frequency is the geometric mean of the upper and lower frequency limits. Inunderwater sound applications, the sound source spectrums are usually represented in the one-third octavebands. The standard one-third octave band center frequencies are defined as: 10, 12.5, 16, 20, 25, 31.5, 40,50, 63, 80 Hz, and factors of 10 times and 100 times of this list of frequencies, and so on.

Pistonphone. An apparatus having a rigid piston which can be given a reciprocating motion of a knownfrequency and amplitude, so as to permit the establishment of a known sound pressure in a closed chamberof small dimensions (Ref: IEC 60565). Also, an acoustical calibrator (sound source) that uses a closedcoupling volume to generate a precise sound pressure for the calibration of measurement microphones. It isto be calibrated using a calibrated microphone if the results are to be traceable.

Quiet Operation Condition. A low-speed operation condition for a vessel operating in environmentally-sensitive areas. The minimum vessel speed in the test for the Quiet Operation is specified in 5/9.1.

Radiated Noise. A vessel’s radiated noise is the acoustic energy radiated into the sea by sources originatingat or within the vessel, from machinery transmitted to the hull/water interface, machinery and flow noisethrough sea-connected piping systems, and hydrodynamic noise caused by the interaction of the ship hull.

Sheet Cavitation. Sheet cavitation is a kind of propeller cavitation. It is generated due to large suctionpressures build up near the leading edge of the blades when the blade sections are working at non-shock-free angles of incidence.

Sound Pressure Level (SPL) (or Sound Level (Lp)). A logarithm measure of the effective sound pressure ofa sound relative a reference value. It is measured in decibels (dB) above a standard reference level whereprms is the root-mean-square sound pressure measured and pref is the reference sound pressure. In water, areference level of one 1 μPa (1.45 × 10-10 psi) is used.

Lp = 10log prms2pref2 = 20log prmsprefSource Level. The apparent strength of a sound source at a nominal reference distance of one meter (3.28feet) from the source and expressed in dB re 1 μPa (1.45 × 10-10 psi) in underwater acoustics.

Start Data Point. The position where the data recording is started when the acoustic center reaches thispoint. It is typically at a distance half DWL ahead of the CPA point. This point is also known as the “BowCPA”. See Section 5, Figure 1.

Section 1 General 1


Starting Point of Test Range. The starting location of a test run at a distance twice the data window length(DWL) ahead of the CPA point. See Section 5, Figure 1.

Tip Vortex Cavitation. Tip vortex cavitation is a kind of propeller cavitation generated from the low-pressure core of the shed vortices. It usually occurs at the blade tips.

Transmission Loss (TL). A measure of the rate of loss in intensity or pressure of the acoustic field strengthas sound propagates from a source to a receptor and is generally defined as:TL = 20log p0pRwhere p0 is the pressure at a point one meter (one foot) away from the source and pR is the pressure atrange R meters (3.28R feet) from the source, orTL = NlogR+ αRwhere N is the coefficient of geometric spreading, R is the range from the source, and α[in dB/m (dB/3.28ft)] is a factor for the absorption of sound in water.

15 AbbreviationsADC: Analog-to-digital converter

CPA: Closest point of approach

DAS: Data acquisition system

DWL: Data window length

DWP: Data window period

EU: European Union

GES: Good Environmental Status

GPS: Global positioning system

ICES: International Council for the Exploration of the Sea

IMO: International Maritime Organization

MCR: Maximum continuous rating

MEPC: Marine Environmental Protection Committee

MSFD: Marine Strategic Framework Directive

Section 1 General 1


S E C T I O N 2 Documentation and Engineering Review

1 Plans and Documentation for InformationThe following vessel plans are required to be submitted to the ABS Engineering Office for information:

● General arrangement drawings with vessel main particulars such as overall length, draft, etc.

● Aft end construction drawings

● Machinery/propulsion arrangement drawings

● Machinery information: manufacturer, model, power, RPM, etc.

● Propeller information: manufacturer, model, propeller diameter, propeller pitch, number of blades,speed, power, etc.

3 Engineering ReviewBefore commencing the underwater noise measurement during sea trials, the drawings/documentsindicated in Section 2, Table 1 are to be submitted to the ABS Engineering Office for review and approval.

After completing the measurement and result post-processing, the final underwater noise measurementreport is to be submitted to ABS Engineering Office for review. The measurement report is to include thecontents indicated in Section 2, Table 2.


TABLE 1 Underwater Noise Measurement Plan

Section 2 Documentation and Engineering Review 2


TABLE 2Underwater Noise Measurement Report

Section 2 Documentation and Engineering Review 2


S E C T I O N 3 Underwater Noise Requirements

1 GeneralThis Section specifies the requirements for the maximum allowable underwater noise limits for specificoperating conditions. The type of criteria is assigned with the Type notation as specified in Subsection 1/3.

The frequency range to be evaluated is between 10 Hz to 50,000 Hz for commercial vessels and 10 Hz to100, 000 Hz for research vessels.

Allowable limits are expressed in one-third octave bands. The unit of the sound pressure level limit is 1μPa @ 1 m (1.45 × 10-10 psi @ 3.28 ft) in this Guide. It means that the sound pressure level is to beevaluated at 1 m (3.28 ft) away from the acoustic center of the vessel, and the reference sound pressure is 1μPa (1.45 × 10-10 psi).

Compliance with the Guide is to be verified through underwater sound measurements.

A maximum 3 dB in excess of the criteria curve at a single one-third octave band is acceptable if theoverall measured noise level of the vessel can meet the criteria specified in this Guide.

Deviations from the requirements, if they can be justified by analysis, may be accepted upon assessmentby ABS (for example, if the narrow band analysis shows the deviations at low frequencies are not relatedto the underwater noise source, but from disturbance of the measuring device due to sea surface effect orfrom interference of another object, such as a metrological sound buoy).

3 Underwater Noise (UWN) Requirements for Commercial VesselsThe maximum allowable UWN limits for commercial vessels in one-third (1/3) octave bands are specifiedin Section 3, Figure 1 and the mathematical definition of the limits is indicated in Section 3, Table 1.


FIGURE 1 Allowable UWN Limits for Commercial Vessels

TABLE 1UWN Limits for Commercial Vessels

Frequency RangeCriteria, Lp, in dB re 1 μPa @1 m (1.45 × 10-10 psi @ 3.28 ft)

Transit Condition Quiet Operation Condition

10 – 100 Hz –1.5 log f + 178.5 –1.5 log f + 170.5

100 – 1 k Hz –6 log f + 187.5 –6 log f + 179.5

1 k – 50 k Hz –10 log f + 199.5 –10 log f + 191.5

5 Underwater Noise (UWN) Requirements for Research VesselsThe maximum allowable UWN limits in one-third (1/3) octave bands for research vessels are given inSection 3, Figure 2 and Section 3, Table 2, which are based on the International Council for theExploration of the Sea (ICES) 209 standard for all free running speeds from 0 knot to 11 knots.

Section 3 Underwater Noise Requirements 3


FIGURE 2Allowable UWN Limits for Research Vessels

TABLE 2 UWN Limits for Research Vessels

Frequency Range Criteria, Lp, in dB re 1 μPa @1 m (1.45 × 10-10 psi @ 3.28 ft)

10 – 1k Hz 135 – 1.66 log f + 10 log(Δf), f in Hz

1 k – 100 k Hz 130 – 22 log f + 10 log(Δf), f in kHz

where Δf is the bandwidth of the measured data.

7 Underwater Noise Plus (UWN+) Requirements for CommercialVesselsThe maximum allowable limits for the UWN+ (Type) notation for commercial vessels in one-third (1/3)octave bands are specified in Section 3, Figure 3, and the mathematical definition is given in Section 3,Table 3.



FIGURE 3 Allowable UWN+ Limits for Commercial Vessels

TABLE 3UWN+ Limits for Commercial Vessels

Frequency RangeCriteria, Lp, in dB re 1 μPa @1 m (1.45 × 10-10 psi @ 3.28 ft)

Transit Condition Quiet Operation Condition

10 – 100 Hz –1.5 log f+ 173.5 –1.5 log f + 165.5

100 – 1 k Hz –6 log f + 182.5 –6 log f + 174.5

1 k – 50 k Hz –10 log f + 194.5 –10 log f + 186.5



S E C T I O N 4 Instrumentation for Measurement

1 IntroductionThis Section outlines the procedures for measurement of the underwater sound emitted by vessels for theassignment of the UWN (Type) or UWN+ (Type) notation.

The key instrumentation components that are used for the measurement of underwater noise include:

i) Hydrophones and their signal conditioning

ii) Sound data acquisition and recording systems

iii) Sound data processing and display systems

“Hydrophone” as used in this Guide refers also to an underwater microphone or electroacoustic transducer.

3 Hydrophones and Signal Conditioning

3.1 Required Characteristics of a HydrophoneThe selected hydrophones that are used to measure the vessel under test are to meet the performancestandard as described in Section 4, Table 1.

TABLE 1Performance Requirements of Hydrophones

Item Specification

Number and Type of Hydrophones At least three omni-directional hydrophones

Hydrophone Sensitivity(Uncertainty)

3 dB (If deviates, the client could submit their assessment of uncertainty based on therecommendation by the instrument manufacturer)

Frequency Span 10 Hz to 50,000 Hz for commercial vessels; 10 Hz to 100,000 Hz for research vessels

Calibration* ● Portable Arrangement: Laboratory calibration every 12 months as well as fieldcalibrated prior to and daily throughout the measurement series.

● Fixed Arrangement: Laboratory calibration before installation. Field calibrationby a comparative measurement utilizing a calibrated underwater sound sourceevery 12 months.

The calibration of all systems is to meet national or international standards, and manufacturerrequirements.

3.3 Deployment of HydrophonesProper deployment of the hydrophone(s) is necessary for the accurate measurement of underwater noiselevels of the vessel.

The hydrophones could be deployed by means of a surface-supported system, such as a floating linesystem from a support vessel, or by utilizing a surface buoy. Other acceptable means include a bottom-


mounted system, which involves an anchor with submerged buoy. Section 4, Figures 1 through 3 show thedifferent hydrophone deployment configurations for the underwater noise measurement.

For the underwater noise measurement conducted in shallow water (see 5/7.1), the hydrophones are to bedeployed by bottom mounted system.

To reduce the measurement uncertainties which could occur due to factors such as surface wave action onthe vessel hull and noise generated from the vessel engines, deployment of hydrophones using either thebottom mounted system (Section 4, Figure 3) or the floating line system such as a surface buoy withindependent recorders (Section 4, Figure 2) are preferred over the deployment method using a supportvessel.

For more accurate measurement results, multiple hydrophones are encouraged to be deployed.

3.3.1 Floating Line Deployment using Surface Supported Systemi) Surface Buoy. The use of the surface buoy aids to create a stand-off distance from the

support vessel. This is useful in minimizing wave slap on the hull.

ii) Suspension Device. This decouples the surface motion from the hydrophone and recorder.

iii) Retrieval Ropes. These help retrieve the wires and hydrophones once the measurementshave been carried out.

FIGURE 1Deployment Using a Support Vessel

Section 4 Instrumentation for Measurement 4


FIGURE 2 Deployment Using a Surface Buoy with an Independent Recorder

The use of the surface buoy with a recorder allows data to be stored locally. The independent, self-recording receiver platform is contained in the surface buoy, and the radio link allows ease ofaccess to store data.

Radar reflectors are often fitted to the buoys to help avoid damage by possible collisions and helpreduce any hazards to ships.



3.3.2 Bottom-mounted System

FIGURE 3Deployment using Bottom Mounted System (Anchor with Sub Surface

Buoy)

3.5 Hydrophone(s) Array Deployment GeometryTo effectively measure the beam aspect (direction of either side of the vessel with respect to the location ofthe hydrophones) of the vessel being tested, the arrangement of the three (3) hydrophones is to be such thatthey hang vertically down in the water column at a depth that results from the 15 degree, 30 degree and 45degree depression angle between the sea surface and the distance from the acoustic center of the vessel tothe hydrophones.

The depth of the hydrophones between the sea surface and its corresponding hydrophone may bedetermined from the following equation:d = tan α × dCPAwheredCPA = maximum of 100 m (328 ft) or overall vessel length (corrected with an accuracy of ±10%)d = depth of the hydrophones (d1,d2,d3) (determined by Pythagorean Theorem), in m (ft)α = 15°, 30°, 45° (α1,α2,α3)

Other hydrophone deployment methods may be considered provided that the requirements as per Section4, Table 1 and the arrangement as shown in Section 4, Figure 4 are met upon satisfactory review by ABS.



FIGURE 4Hydrophone Array Deployment with Respect to Vessel under Test

3.7 Signal ConditioningThe types of electronic devices used for signal conditioning are to be carefully considered so that the dataacquisition system effectively and accurately records the mechanical signals produced by the hydrophones.These devices include, but are not limited to, the amplifier, filters, sensor excitation, isolation used with theattenuation, and sampling method input configuration.

5 Data Acquisition and RecordingThe sound data acquisition system (DAS), which consists of the DAS hardware, sensors and actuators,signal conditioning hardware, and a computer running the DAS software, is to be capable of acquiring,recording, and converting physical parameters such as the analog signals from the hydrophones to digitalrepresentations before being manipulated by the digital equipment.

The DAS is also to be able to obtain the position data of the support vessel or the surface buoy, for instancea global positioning system (GPS) or radar. The position of both the vessel under test and the supportvessel or surface buoy (whichever is employed as the means for the deployment of the hydrophones) is tobe recorded at the time where the measurement is being carried out. Recording systems are to besynchronized to GPS accuracy before deployment and re-checked after retrieval.

The DAS is to have an appropriate sampling rate of at least 2.5 times of the exact center frequency of thehighest frequency band.

As appropriate, all the individual equipment/components in the DAS are to be calibrated to a known outputlevel before and after every major deployment or sea trial.

The information regarding the methods and the instrumentation specification (calibration, accuracy, andsensitivity) that are used for data collection, as well as the means to enable accurate data recording, are tobe provided.



7 Sound Data Processing and Display SystemThe data processing system (broadband and narrow band) is to be capable of analyzing the sound level toobtain the required data output for the noise assessment as per 5/13.

The broadband processing of the underwater radiated noise is to cover the one-third octave band frequencyrange from 10 Hz to 50,000 Hz for commercial vessels and 10 Hz to 100,000 Hz for research vessels. Thedata processing is to include using the one-third band filters in accordance with Class 1 requirements ofIEC 61260.

The narrow band processing is to be in appropriate bandwidths relative to the frequencies. This is usuallymeasured at each 1 Hz frequency. The narrow band processing is to cover a frequency range from 10 Hz to5000 Hz or higher. Narrow band data can be used for diagnostic purposes as it allows the opportunity toidentify specific tones in the noise since the peaks in the measured spectrum can be used to distinguishmachinery and systems that are expected to produce identical tones.

Details with regard to the methods, software, and instrumentation used for data analysis of the receivedacoustic data are to be provided.



S E C T I O N 5 Underwater Noise Measurement and Survey

1 GeneralThis Section describes the details of the acoustic measurement procedures to be carried out for themeasurement of the underwater radiated noise.

1.1 Measurement ProtocolsThe establishment of the underwater noise measurement procedure (measurement plan preparation, testmeasurement procedures and/or test reporting) used in this Guide are based on the information provided inthe following reference documents.

TABLE 1Current Underwater Noise Measurement Standards and Other Related

Measurement Standards

International Recognized Standards

ANSI/ASA S12.64-Part 1, 2009 Quantities and Procedures for Description and Measurement ofUnderwater Sound from Ships-Part 1: General Requirements

ISO/PAS 17208-1:2012, Part I Acoustics-Quantities and procedures for description and measurement ofunderwater sound from ships - Part 1: General requirements formeasurements in deep water

ICES Cooperative Research Report No. 209 Underwater Noise of Research Vessels, Review and Recommendation

IEC 61260 Electroacoustics – Octave band and fractional-octave band filters

IEC 60565 Underwater acoustics – Hydrophones - Calibration in the frequencyrange 0,01 Hz to 1 MHz

ANSI/ASA S1.11 Specification for Octave-band and Fractional-octave-band Analog andDigital Filters

ANSI/ASA S1.20 American National Standard Procedures for Calibration of UnderwaterElectroacoustic Transducers

ISO/IEC Guide 98-3 Uncertainty of Measurement – Part 3 Guide to the Expression ofUncertainty in Measurement

1.3 Measurement PlanThe measurement plan is to serve as the principal means of verifying the measurements to be performed todemonstrate compliance with the ABS underwater noise criteria.

The proposed measurement plan is to be submitted to and approved by the ABS Engineering Office priorto performing the underwater noise measurements. Upon review by the ABS Engineering Office, the shipowner or shipyard will then be notified whether the measurement plan has been approved or requiresfurther alteration.

A detailed description of the drawings and information to be included as part of the measurement plan isindicated in Section 2, Table 1.


1.5 Background Noise MeasurementBackground noise is usually a combination of noise from both environmental and man-made sources, andthus is highly variable temporally and spatially.

It is therefore important to determine the background noise level (which is usually present during themeasurement at a certain location) so that this can be distinguished and eliminated from the results of thetotal measured underwater sound pressure level at the end of the test period, allowing for the actualunderwater noise measurement to be determined.

1.7 Distance MeasurementTo measure the underwater radiated noise, it is necessary to acquire the sound pressure measurement at adistance from the sound source and to correct for propagation loss to produce an estimation of the soundpressure level at a reference distance [i.e., 1 m (3.28 ft)].

For the purpose of this Guide, the distance measurement is to be taken between the horizontal distance ofthe location of the sea surface above the hydrophones and the acoustic center (halfway between the centerof the main engine room and the propeller) of the vessel under test, at the CPA.

The accuracy of the distance measurement system shall be within 10% of the distance at the CPA.

1.9 Performance of Underwater Noise MeasurementThe underwater noise measurement is to be executed by an ABS Recognized External Specialist forUnderwater Noise Measurement (see 5/3).

The ABS Surveyor is to sign the underwater noise measurement data sheet verifying that themeasurements were carried out according to the measurement plan approved by ABS.

1.11 Other Auxiliary Measurements and DataInformation that may affect the sound propagation during the measurement test period, and thereforeaccuracy of the final measurement of the underwater noise levels, is recommended to be recorded.

Taking note of the following parameters and information helps to avoid noise contamination with therecording of the underwater noise. This data would also be useful when explaining the deviation (if any) ofthe final resulting sound signature. Refer to Section 5 of this Guide for more details.

This information includes, but is not limited to, the following:

i) Sea state conditions:

● Seabed composition

● Water column acoustic properties (salinity, water temperature, and density that varies with thewater depth to derive the sound speed)

● Tidal deviations in water depth

ii) Weather conditions:

● Rainfall

● Wind direction and speed

● Wave height in relations to the wind speed

iii) Shipping activities near the vicinity:

● Presence of any vessels (their speed, size, and distance from the test site area) operating in theacoustic range/vicinity of the test site

● This could be achieved by means of an Automatic Identification System data

Section 5 Underwater Noise Measurement and Survey 5


● Presence of any distant noise-generating industrial activity (seismic exploration or offshoreconstruction such as wind farms and hydrocarbon production activities)

iv) Locations of the hydrophones, observation vessel, and recording systems

v) Depth of the hydrophones in the water column

vi) Operating conditions of vessels to be tested (speed, draft, machinery configuration, engine output)

vii) Distance of the vessel under test from the harbor

3 ABS Recognized External Specialist for Underwater NoiseMeasurementThe measurement plan is to include information of the ABS Recognized External Specialist forUnderwater Noise Measurement who is appointed by the ship owner/shipyard to conduct the underwaternoise measurement.

In order to perform underwater noise measurement for ABS survey purposes, the service provider is tobecome an ABS Recognized External Specialist. The specialist is to provide evidence/documentationdemonstrating their capability/knowledge based on their experience and expertise in the field ofunderwater noise measurements. The documents are to include the specialist’s experiences in conductingthe underwater noise measurement to show that it has been carried out in accordance to recognizednational, international, or industry standards, as applicable, as indicated in Section 5, Table 1.

A description of the acoustic equipment and facilities used for carrying out the underwater noisemeasurement, data collection, data analysis, and post processing of the collected measurements data setsfor which approval is sought (e.g., calibration, accuracy, sensitivity, etc.) is also to be provided as part ofthe documentation. This information is to include, but is not limited to, the details of the manufacturer,type and serial number, accuracy, sampling frequency and resolution of the measurement and analysisequipment, and the last maintenance schedule dates. Copies of relevant instrumentation referencecalibration certificates, with traceability to a national or international standard are also to be part of thedocumentation.

The specific requirements for the acoustic equipment are:

● Requirements for the performance and calibration of the hydrophones as indicated in Section 4, Table1.

● Requirements for the DAS system as indicated in 4/5.

● Requirements for the data processing system as indicated in 4/7.

● Requirements for the accuracy of the distance measurement system as indicated in 5/1.7.

Further requirements for becoming an ABS Recognized External Specialist for Underwater NoiseMeasurement can be obtained from the ABS Programs Office or the local ABS office.

5 SurveyThe underwater noise measurement and the data collection process are to be executed by an ABSRecognized Underwater Sound Specialist and witnessed by an ABS Surveyor. The test personnel are tocomplete the Underwater Noise Measurement Data Sheet (Appendix 2) at the time of the survey.Equipment and instrumentation reference calibration certificates, together with the results of the field setupand calibration check, are to be provided to the ABS Surveyor.

7 Test Site RequirementsThe location of the measurement test site is to be determined by the ship owner, shipyard and approved byABS before any measurement is carried out. The key factors to consider when selecting a suitable test site



are the geographical location and the seasonal weather when carrying out the planned acousticmeasurement activity.

Other factors include, but are not limited to, salinity, water temperature, water depth, sea conditions,weather conditions, a safe zone (for the safety and ability of the vessel under test to maneuver taking intoaccount the sea traffic in the vicinity; distance from shore (prevent unwanted reflections), and lowbackground noise (considering the surrounding shipping activities at or near the vicinity of the proposedtest site).

7.1 Depth of the WaterFor the underwater noise measurement to be conducted in shallow water (water depth less than 150 m (492ft)), the minimum water depth requirement (from the keel of the vessel under test) is to be 60 m (196.8 ft)or 0 . 3ν2m 0 . 26ν2 ft , where ν is the vessel speed in m/s (knots), whichever is greater. The sea floor atthe test site is to be as flat as possible.

For the underwater noise measurement to be conducted in deep water and in a far-field condition, theminimum water depth requirement (from the keel of the vessel under test) is to be at least 150 m (492 ft) or1.5 times of the overall vessel length, whichever is greater.

7.3 Weather/Sea Surface ConditionsSevere/rough weather and sea surface conditions can result in numerous problems such as increasing thebackground noise and causing the vessel under test or the observation vessel (if used as the means fordeployment of hydrophones) to be unstable and thus require the continuous running of the main engine andits propulsion system to maintain its orientation.

The measurements are to be taken under conditions of Sea State 3 or less with a maximum wind speed ofBeaufort number 4.

9 Test Conditions of Vessel

9.1 Operation ConditionThe measurements are to be carried out as specified in the proposed measurement plan.

The operation condition of Transit or Research Vessels is to be decided by contractual service condition, orwith the main and auxiliary engines to run at least 85% of MCR. For vessels fitted with controllable pitchpropellers the measurements are to be carried out in the normal operating condition.

The minimum vessel speed in the measurement for Quiet Operation is to be:νquiet, min = 3 . 1 + 0 . 0084 Loa SI units= 6 + 0 . 005 Loa US unitswhereνquiet, min = minimum vessel speed in the test for the Quiet Operation, m/s (knots)Loa = overall length of the vessel, m (ft)

9.3 Loading ConditionThe measurements are to be carried out under a representative loading condition that is reviewed andapproved by ABS. The propeller is to be fully submerged.



9.5 Test CourseThe vessel is to maintain a straight path on a predetermined course at a constant speed, without excessiverudder actions.

11 Measurement Test Sequence

11.1 GeneralAn example of an underwater noise measurement configuration in a beam aspect test course is shown inSection 5, Figure 1.

To achieve the required distance at the CPA between the vessel under test and the hydrophones, the vesselis to maintain a straight line sailing course.

At the Starting Point of Test Range, the required vessel test conditions need to be in place. This includesminimal rudder actions, and maintaining a constant speed and direction, and fixed machineryconfigurations.

The Starting Point of Test Range is two times the data window length before the distance of the CPA. TheEnding Point of Test Range is marked as two times the data window length after the distance of the CPA.

From the beginning to the end of the data recording period, also known as the data Window Length(DWL), the operating conditions of the vessel are to remain unchanged.

FIGURE 1Underwater Noise Measurement Configuration – Beam Aspect Test Course

11.3 Sea Trial ProcedureThe underwater noise measurements are to be carried out accordingly to the ten steps in a sequential order,as described in 5/11.5.



To reduce the uncertainty due to propagation losses, the test course is to include a total of four (4) repeatedruns with alternating runs on each side (port and starboard) of the vessel to be performed for each vesseloperational conditions.

The vessel under test typically makes several passes by the array, in order to average port and starboardaspect radiated noise abeam of the vessel. In this Guide, the measurement data are to be collected at eachof the three (3) individual hydrophones for four measurement runs being kept separately, two runs at portand two runs at starboard.

These collected data sets are to go through a post-processing phase as described in 5/13 to account for theunwanted background noise, sensitivity adjustment, and propagation/transmission losses.

The radiated underwater noise intensity spectrum obtained from the twelve data sets is the arithmeticallyaverage to provide an overall averaged one-third spectrum.

11.5 Underwater Noise Measurement Test Sequencei) The main propulsion and auxiliary machinery conditions are to be set up according to the

conditions as specified in the measurement plan approved by ABS (Section 2, Table 1 and 5/1.1).The same is to be verified by the ABS Surveyor.

ii) The hydrophones and measuring instruments used in the data acquisition system are to becalibrated prior to the underwater noise measurements. The relevant instrumentation referencecalibration certificates, together with the results of the field setup and calibration check are to beprovided to the ABS Surveyor.

iii) The ABS Recognized External Specialist for Underwater Noise Measurement is to verify that allthe measurement systems for carrying out the underwater radiated noise measurement are put inplace and are functioning correctly.

iv) At the start and the end of each measurement test run, the background noise measurement is to becarried out and recorded for at least 1 minute with the vessel under test located at the farthestdistance or at a distance of at least ≥ 2000 m (approximately 1.08 nautical mile) from thehydrophones, with the same hydrophone deployment and data acquisition methods.

v) During the recording of the background noise measurement, all main engines and generators are tooperate only in idle conditions.

vi) After the completion of the background noise measurement, the vessel under test is to proceed tooperate at the prescribed operating condition as specified in the approved measurement plan. Theoperating conditions such as the main and auxiliary engine output, vessel speed, propeller RPMand nominal pitch, and loading condition are to be recorded accordingly.

vii) Before the acoustic center of the vessel reaches the Starting Point of Test Range, the desiredoperating conditions of the vessel under test are to be achieved. Between the Starting Point of TestRange and the Ending Point of Test Range, the direction and vessel operating conditions are toremain the same.

viii) The data recording of the test measurement for the radiated underwater noise (where themechanical output signal of the hydrophones is sent to the data acquisition system) is only tocommence when the position of the acoustic center of the vessel under test reaches the start datapoint (beginning of the data window period) and is to terminate when the acoustic center of thevessel under test reaches the end data point (end of the data window period) as shown in Section5, Figure 1.

ix) Distance measurements are to be recorded for the vessel under test. These include the distance atthe closest point of approach (dCPA), horizontal distance from the acoustic center of the vessel toeach hydrophone and the vertical distance between the depth of each hydrophone and the seasurface.



x) The vessel under test is to make a “Williamson Turn” at the Ending Point of Test Range, where thevessel will maneuver and prepare for the next set of runs on the alternate side of the vesselrepeating the measurement procedure vi) to ix).

A complete test course requires the vessel under test to perform two (2) repeated runs (with alternatingapproach) each on the port and starboard side of the vessel under the same operating conditions.

13 Processing and Analysis of Measured DataThe measured underwater radiated sound pressure level from the vessel under test is to undergo a post-processing phase to account for background noise adjustment, sensitivity adjustment and distancecorrection.

The underwater radiated sound pressure level, which is collected during the data window period (DWP), isto be filtered and applied with the root mean square linear averaged [expressed in terms of dB re 1 μPa(1.45 × 10-10 psi)] in one-third octave bands, as well as in the narrow band spectrum for each run of themeasurement.

13.1 Background Noise CorrectionA set of background noise data is to be collected at the beginning and at the end of each measurement run.This is to enable the comparison of the sound pressure level radiated from the vessel under test to thebackground noise level during the period of the measurement test.

The background noise collected during the data window period (DWP) is to be filtered and applied withthe root mean square linear averaged (expressed in terms of dB re.1 μPa (1.45 × 10-10 psi) in one-thirdoctave bands as well as in the narrow band spectrum each run of the measurement.

The signal-plus-noise-to-noise ratio, ΔL, for each 1/3 octave band is calculated as shown in Equation 1.

Depending on the output of the signal-plus-noise-to-noise ratio, the following conditions in Section 5,Table 2 will apply according for the measured underwater sound pressure level of the vessel under test.

TABLE 2 Signal-Plus-Noise-to-Noise Ratio Conditions

Signal-Plus-Noise-to-Noise Ratio ConditionsΔL > 10 dB No background noise correction would be required. See Equation 2

3 dB ≤ ΔL ≤ 10 dB Background noise correction is to be applied to the measured underwater soundpressure level. See Equation 3

ΔL < 3 dB The measured underwater sound pressure level results might be considered as aninvalid data ABS would evaluate and consider the validity of the data depending on acase-by-case basis.Signal‐plus‐noise‐to‐noise ratio, ΔL ΔL = Lps+ n – Lpn = 10log ps+ n2pn2 1For ΔL > 10 dB Lp = Lps+ n 2For 3 dB ≤ ΔL ≤ 10 dB Lp′ = 10log 10 Lps+ n/10 − 10 Lpn/10 3

whereΔL = signal-plus-noise-to-noise ratiops+ n = total underwater sound pressure received at the hydrophones, in μPa (psi). This includes both theunderwater radiated sound from the vessel under test and the unwanted background noise.



pn = sound pressure of the background noise received at the hydrophone, in μPa (psi)Lps+ n = sound pressure level of the vessel under test for each run, in dBLpn = background sound pressure level taken with the vessel under test being at a distance of 2 km (6560 ft)away from the hydrophones, in dBLp = underwater sound pressure level that do not require background noise correction, in dB re 1μPa (1.45 ×10-10 psi)Lp′ = underwater sound pressure level, adjusted to include the background noise correction, in dB re 1μPa(1.45 × 10-10 psi)

13.3 Bottom Effect CorrectionIf the distance between the hydrophone and the bottom is less than 0.2 m (0.66 ft), a 5 dB reduction to theunderwater sound pressure level can be made to correct for the sound reflection from the sea bottom.

13.5 Sensitivity AdjustmentThe adjusted underwater sound pressure level Lp′ taken into account the background noise correction, isalso required to consider the sensitivity aspect of the hydrophone(s) using Equation (4).Lp" = Lp′ + HSEN 4whereLp" = underwater sound pressure level, adjusted to include the hydrophones sensitivity correction, in dB re

1μPa (1.45 × 10-10 psi)Lp′ = underwater sound pressure level, adjusted to include the background noise correction, in dB re 1μPa(1.45 × 10-10 psi)HSEN = hydrophones sensitivity correction (between 1.5 to 2 dB).

13.7 Distance CorrectionThe final underwater sound pressure level, LS r, i is to account for the transmission loss that is to becorrected to a reference distance of 1 m (3.28 ft) for each hydrophone and measurement run usingEquation (5).LS r, i = Lp" + TL 5WhereLS r, i = final underwater sound pressure level corrected to a reference distance of 1 m (3.28 ft) based on each

run (r) and for each individual hydrophone ( i= 1, 2, 3), in dB re 1μPa @ 1 m (1.45 × 10-10 psi @ 3.28ft)Lp" = underwater sound pressure level, adjusted to include the hydrophones sensitivity correction, in dB re1μPa (1.45 × 10-10 psi)TL = transmission loss due to the sound propagation through the deep water from the source to the receiver(hydrophones), in dBTL can be obtained by the measurement, numerical calculation or simple propagation law using Equations

(6) and (7). When measuring the transmission loss directly, the known source is to be towed along the



same path as the vessel under test. For numerical estimation, it is necessary to consider the geo-acousticproperties of the sea bottom.TL − 20log DTotalDref 6DTotal = Dvertical2 + Dℎorizontal2 7whereDTotal = total distance from the acoustic center of the vessel under test to each of the hydrophones, in m (ft)Dvertical = depth of the hydrophone from the sea surface, in m (ft)Dℎorizontal = horizontal distance from the sea surface above the hydrophone(s) to the acoustic center of the

vessel under test, in m (ft). This distance could be verified by means of using any distancemeasurement device (i.e., laser rangefinder, ultrasonic ranging module (sonar, echo-sounding),radar distance measurement, or a GPS system).Dref m = standard reference of distance = 1 m (3.28 ft).

13.9 Power-averaged of the Sound Source Level from all HydrophonesLS r = 10log 10LS r, 1 /10 + 10LS r, 2 /10 + 10LS r, 3 /103 8whereLS r = power averaged of the sound source level received from the three hydrophones for each test run

number, r (r being r1, r2, r3, and r4), at a reference distance of 1 m (3.28 ft).LS r, i = underwater sound source level received from the each hydrophone for test run number, r (r beingr1, r2, r3, and r4). See Section 4, Figure 4.

13.11 Arithmetic Average of the Sound Source Level of the Four Runs under the SameOperation ConditionThe results from the test runs data are to be arithmetically averaged using Equation (8) to establish theresulting signature source level for the vessel under a specific operating condition when the measurementruns are carried out.

For different operating conditions, the resulting signature source level value, LS, is to be determinedseparately.LS = ∑r = 1r = kLS r /n 9whereLS = resulting signature source level for n number of runsLS r = power averaged of the sound source level received from the three hydrophones for each test run

number, r (r being r1, r2, r3, and r4), at a reference distance of 1 m (3.28 ft).n = 4 (total number of runs).



15 Measurement ReportUpon completion of the underwater noise measurement and measurement data post processing, themeasurement report is to be submitted to the ABS Engineering Office. The specific contents to be includedin the underwater radiated noise measurement report are outlined in Section 2, Table 2.



A P P E N D I X 1 Underwater Noise Control

1 IntroductionA good rule of underwater noise control is to use equipment with lower noise and/or vibration level.Propellers and machinery equipment are two dominant underwater noise sources. The noise control of thetwo sources can effectively reduce the underwater noise emitted by vessels. This Section introduces somebasic approaches for the selection, design, installation and maintenance of quieter propellers or machineryequipment.

3 Propeller Noise ControlPropeller cavitation can generate excessive noise. Therefore, an important noise control approach is tooperate a vessel below the propeller cavitation inception speed. A well-designed propeller can have arelatively high cavitation inception speed, which makes it less susceptible to cavitation.

In order for a propeller to have a good acoustic performance, it is also important to have a sufficientclearance between the blade tips and the hull of the vessel, and have smooth inflows of water into thepropeller. In addition, cleaning and maintenance of propeller are critical to underwater noise control.Propellers with dings, missing sections, barnacles, etc., can be significantly louder than a clean propeller inits original form.

The following are some general design guidelines for quieter propellers:

● Increasing propeller diameter and reducing rotation rate can generally increase the cavitation inceptionspeed

● Increasing the number of blades can delay inception of tip vortex cavitation and thicker blade sectionscan be used to delay the inception of sheet cavitation

● A well-designed skewed propeller shape can normally have a better acoustic performance

● Adjusting blade pitch distribution to unload tip can reduce cavitation

5 Machinery Equipment Noise ControlWhen selecting quieter machinery equipment, the following guideline can be used:

● Rotating equipment is usually quieter than reciprocating equipment

● Drip-proof electric motors are usually quieter than totally enclosed fan-cooled motors

● Pumps operating at their most efficient design point are less noisy than those operating off design

● Generally, gas turbines are quieter than diesel engines and produce lower vibration levels

Once a piece of machinery is selected, it needs to be properly installed on a foundation with enoughstiffness. The natural frequency of the foundation should not coincide with the excitation frequency of theequipment. For machinery equipment with a higher vibration level, it is recommended to install isolationsor resilient mounting system between the equipment and foundation to reduce the structure-borne noisecaused by machinery vibration.


A P P E N D I X 2 Underwater Noise Measurements Data Sheet


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Appendix 2 Underwater Noise Measurements Data Sheet A2


A P P E N D I X 3 References

1) IMO MEPC 57/INF.4, 2007, Shipping Noise and Marine Mammals, Submitted by the UnitedStates to the Marine Environment Protection Committee, 57th Session

2) IMO MEPC.1/Circ.833, 2014, Guidelines for the Reduction of Underwater Noise fromCommercial Shipping to Address Adverse Impacts on Marine Life

3) EC 2010, Commission Decision of 1 September 2010 on criteria and methodological standards ongood environmental status of marine waters (2010/477/EC), Official Journal of the EuropeanUnion

4) EU Directive 2008/56/EC of 17 June 2008, Establishing a framework for community action in thefield of marine environmental policy (Marine Strategy Framework Directive), Official Journal ofthe European Union

5) ANSI/ASA S12.64-2009, Quantities and Procedures for Description and Measurement ofUnderwater Sound from Ships, Part 1: General Requirements

6) ISO/PAS 17208-1-:2012 – Acoustics – Quantities and procedures for description andmeasurement of underwater sound from ships – Part 1: General requirements for measurements indeep water

7) ICES Cooperative Research Report No. 209, May 1995, Underwater Noise of Research Vessels,Review and Recommendation, R.B. Mitson

8) World Meteorological Organization-No. 306 (1995). International Codes Vol I.1 Part AAlphanumeric Codes. Geneva, Switzerland

9) International Electrotechnical Commission. (2014). Electroacoustics – Octave band and fractional– octave band filters (International Standard IEC 61260) (Note: Reference by ANSI)

10) International Electrotechnical Commission. (2006). Underwater acoustics – Hydrophones –Calibration in the frequency range 0,01 Hz to 1 MHz (International Standard IEC 60565)(Note:Reference by ANSI)

11) ANSI/ASA S1.11 (2014), Specification for Octave-band and Fractional-octave-band Analog andDigital Filters

12) ANSI/ASA S1.20 (2012), Procedures for Calibration of Underwater Electroacoustic Transducers(Note: Reference by ANSI)

13) ISO/IEC Guide 98-3 (2008), Uncertainty of Measurement – Part 3 Guide to the Expression ofUncertainty in Measurement

14) OSPAR Commission (2009), Overview of the Impacts of Anthropogenic Underwater Sound In themarine Environment, Publication number 441/2009

15) OSPAR Commission (2009), Assessment of Environmental Impact of Underwater Noise,Publication number 436/2009

16) NPL Good Practice Guide No. 133 (2014), Underwater Noise Measurement

17) EMEC report (2012), Acoustic Noise Measurement Methodology for the Billia Croo Wave EnergyTest Site

18) EMEC report (2014), Underwater Acoustic Monitoring at Wave and Tidal Energy Sites: GuidanceNotes for Regulators


19) DSTL Naval Systems (2011), Quality Assurance Assessment of a Study into Underwater RadiatedNoise From Marine Aggregate Dredging Operations For the Marine Aggregate LevySustainability Fund

20) David L. Bradley and Richard Stern, 2008, Underwater Sound and the Marine Mammal AcousticEnvironment, A Guide to Fundamental Principles

21) Megan F. McKenna, 2012, Underwater Radiated Noise from Modern Commercial Ships

22) Brown, N., “Cavitation Noise Problems and Solutions,” International Symposium on ShipboardAcoustics, J. H. Janssen (ed.), Elsiver Scientific Publications, Amsterdam, 1976.

23) R. W. Fischer, C. B. Burroughs and D. L. Nelson, Design guide for shipboard airborne noisecontrol, New York: The Society of Naval Architects and Marine Engineers, 1983.

Appendix 3 References A3


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